Puzzling Human Relative Homo Naledi May Have Lived at the Same Time as Our Ancestors

Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Hawks et al. in eLife, 2017

It's tempting to think that evolution works in a straight line, with clearly defined, graduated steps from primitive to modern. We humans are especially prone to telling our own evolutionary story in this manner. Evolution doesn't work that way, though, and we aren’t even the end point of human evolution, but works in progress. (Personally, I hope we are amphibious and have fins in 3 million years. That would be awesome.)

The latest evidence for that essential truth comes from the Rising Star cave system in South Africa, where scientists say Homo naledi, the unusual hominid species they discovered there in 2013, is surprisingly young, living as recently as 236,000 years ago. That means it was one of various hominids wandering the Earth at the same time as the Neanderthals in Europe; the Denisovans in western Asia; the ancestors of the “hobbit,” Homo floresiensis; and, in Africa, potentially alongside the earliest members of our own species, Homo sapiens.

Moreover, the researchers found three more individuals in another chamber in the cave system, one of them with the most complete H. naledi skull discovered yet. (You can see it above.) Today the large team of researchers published a trio of papers documenting their results in the open-access journal eLife.

In 2015, we reported on the initial discovery of 15 sets of hominid remains found in the Dinaledi cave by a team of researchers led by paleoanthropologist Lee Berger. It was an unprecedented bounty of bones. Often, paleoanthropologists are reconstructing human evolutionary history from scant remains—a fragment of skull or jaw bone here, a femur or a finger there. But in the Dinaledi cave, there are at least 1500 bones, and likely a lot more, since only a small fraction of the cave was excavated by a half-dozen archaeologists—all female, all cavers, all slim enough to squeeze through a series of cave tunnels that narrowed to just 7 inches in one spot—who worked in extraordinary conditions to excavate the bones from a pitch-black cave nearly 100 feet beneath the surface.

The ancient creatures were no bigger than the small but formidable women who unearthed them. Slender and about 5 feet tall as adults, they would’ve weighed just under 100 pounds. Their bodies are a fascinating mosaic of primitive and modern: tiny, orange-sized brains housed in skulls with jaws and teeth closer to early Homo; shoulders suited for climbing trees but feet and ankles made for walking; hands potentially capable of making tools, but with fingers well-curved for tightly gripping tree branches.

The discovery made headlines worldwide. Most of us—whether scientist or science nerd—fascinated by the find had one question: How old were they?

DATING THE REMAINS

When H. naledi was first discovered, the researchers deliberately didn’t attempt to answer that question. Determining where a species fits into the evolutionary record based on its morphology is not an unusual approach, but it can also be misleading. In the past 1.5 years, other scientists have proposed ages for H. naledi that range from 100,000 to 2 million years ago.

In one of the current studies, researchers led by James Cook University geologist Paul Dirks conducted six dating tests to narrow the age range, including the paleomagnetic dating of calcite left behind by running water and a chemical analysis of three fossil teeth discovered in the cave using a technique called combined U-series and electron spin resonance (US-ESR) dating. From all the tests, they came up with an age range: they're most likely between 236,000 and 335,000 years old.

As eLife notes in a commentary on the study, “The estimated dates are much more recent than many had predicted, and mean that H. naledi was alive at the same time as the earliest members of our own species—which most likely evolved between 300,000 and 200,000 years ago. These new findings demonstrate why it can be unwise to try to predict the age of a fossil based only on its appearance, and emphasize the importance of dating specimens via independent tests.”

American Museum of Natural History paleoanthropologist Ian Tattersall echoed that sentiment to Mental Floss. “This is an object lesson in trying to date anything by what it looks like,” he says. While he doesn't find the age estimate surprising, he’s less convinced that H. naledi belongs in our Homo genus: “Anything as odd as this is always going to be tough to fit into both a phylogeny and a timescale,” he notes.

Did our ancestors interact with this oddball? We have no idea. But we do know that the picture of human evolution continues to expand in detail and complexity with every discovery like H. naledi.

Bioarchaeologist (and regular Mental Floss contributor) Kristina Killgrove, who teaches biological anthropology, human origins, and evolutionary theory at the University of West Florida, tells us that the long wait for H. naledi dates was “worth it.”

She says, “These dates reveal a much more complicated story of hominin evolution than ever before. We used to think of human evolution as a single lineage—the classic image of the progression from apes to humans. But H. naledi shows that palaeoanthropologists are onto something far more complex—and far more interesting! While these new dates won't make it into textbooks in time for the fall semester, I will certainly be updating my human evolution lectures this summer."

ONE NEW CAVE, THREE NEW BODIES

Whatever we have to learn about this cousin of humanity can only be helped by the other discovery reported today in eLife: 133 bones from three likely H. naledi individuals—two adults and one child—found in another cave in the Rising Star system. First spotted in 2013 by cavers, the bones were unearthed in three locations in a cave the researchers coined Lesedi. The two caves are found at the same depth, but they’re not directly connected.

As with the first expedition into the Dinaledi cave, the working conditions for the researchers weren’t easy: Wits University archaeologist Marina Elliott, who led the intrepid team of “underground astronauts” who excavated both sites, told National Geographic that while the Lesedi cave was slightly easier to reach than Dinaledi, she still had to excavate one set of remains from a 2-foot-wide alcove while laying on her chest, her shoulders pinned between rocks. “It’s extremely physically difficult,” she said. “I’ve tried to do a lot of yoga to get myself to be able to do it.”

Elliott would probably say it was worth it, though; the remains she excavated in that location yielded the most complete H. naledi skull so far discovered. Dubbed Neo (after the Setswana word for "a gift," not the The Matrix character), this adult has a larger skull—and therefore a larger brain capacity—than the other specimens so far discovered, but it falls within an expected range.

ARE THESE BURIALS OF A SORT?

One of the most contentious theories Berger and the team proposed when the first H. naledi fossils were discovered was that these bodies had been intentionally placed in the cave in some sort of death ritual. Berger and John Hawks, a paleoanthropologist at the University of Wisconsin, revisit that theory in the third paper published in eLife. They point out that the caves are difficult to access and aren’t obvious “death traps” that individuals could’ve accidentally fallen into. Nor did the remains show any signs of mass death, having been fed upon by carnivores or scavengers, or of having been flushed into the caves by a water system.

So how did they get there?

The researchers write, “We propose that funerary caching by H. naledi is a reasonable explanation for the presence of remains in the Dinaledi and Lesedi Chambers. Mortuary behaviors, while culturally diverse, are universal among modern human cultural groups. Such behaviors are not seen in living non-human primates or in other social mammals, but many social mammals exhibit signs of grief, distress, or other emotional response when other individuals within their social group die.”

They say that while there’s no evidence of symbolic thinking among H. naledi, such sophisticated thought isn’t necessarily a requirement for a death ritual. The “physical and social effects of the deaths of group members” could have been motivation enough.

“Such behavior may have many different motivations, from the removal of decaying bodies from habitation areas, to the prevention of scavenger activity, to social bonding, which are not mutually exclusive,” they note. “We suggest only that such cultural behavior may have been within the capabilities of a species that otherwise presents every appearance of technical and subsistence strategies that were common across the genus Homo.”

A WWII Navy Submarine, Lost for 75 Years, Has Been Discovered Off the Coast of Japan

MR1805/iStock via Getty Images
MR1805/iStock via Getty Images

The U.S. Navy lost 52 submarines during World War II, many of which are still missing today. But as The New York Times reports, the wreck of the U.S.S. Grayback—a submarine that disappeared along with its 80-person crew in 1944—has been found off the coast of Okinawa, Japan.

On January 28, 1944, the Grayback departed from Pearl Harbor for its 10th combat patrol. It missed its scheduled return date that spring, and after weeks of failing to locate the vessel, the Navy declared it was likely lost.

Immediately following World War II, the U.S. military studied Japanese war records in search of clues that might lead them to their missing ships. One recording clearly states the Grayback was brought down by a bomb dropped by an Japanese aircraft, and it even gives the longitude and latitude of the attack. But due to a poor translation of the audio, the Navy went looking for the sub 100 miles away from its actual resting place.

Seventy-five years later, the submarine's coordinates were finally uncovered in old Imperial Japanese Navy files.

A Japanese researcher named Yutaka Iwasaki noticed this error while looking at the World War II records of the Imperial Japanese Navy base at Sasebo. He was asked to review the files for the Lost 52 Project, an organization dedicated to finding lost World War II submarines. Using the newly uncovered information and an autonomous underwater vehicle, the team was able to locate the vessel at the bottom of the East China Sea near Okinawa.

Lost 52 doesn't hunt for submarine wrecks with plans to recover them. Rather, the goal of the project is "documenting and preserving the story of the Lost 52 WWII Submarines, leaving a foundation of knowledge for future generations." In the case of the Grayback, the site where it settled on the seafloor will be protected from any human interference.

[h/t The New York Times]

Swedish Divers Just Discovered Two Shipwrecks That Might Be Related to the Famous Vasa Warship

The Vasa shipwreck displayed in Sweden's Vasa Museum.
The Vasa shipwreck displayed in Sweden's Vasa Museum.
Christian Lundh, Flickr // CC BY-NC 2.0

In 1625, King Gustavus II Adolphus of Sweden commissioned shipbuilders to create the most beautiful, lethal flagship that ever existed, as a symbol of Sweden’s naval strength. Three years later, crowds gathered to watch the Vasa, named after Sweden’s royal house, set sail for the first time. But less than a mile into its maiden voyage, the poorly and hastily constructed warship sunk to the bottom of the Baltic Sea, where it remained until 1961 when it was salvaged and later transported to the Vasa Museum.

Now, the Guardian reports Swedish maritime archaeologists from Vrak—Museum of Wrecks have located two shipwrecks in the Swedish archipelago outside of Vaxholm that could be linked to the Vasa. This is because the shipwright responsible for the Vasa built three other ships, the Äpplet, the Kronan, and the Scepter (though, unlike their ill-fated sibling, they actually made it into battle).

“It was like swimming around the Vasa ship,” maritime archaeologist Jim Hansson said in a museum press release. They believe the first wreck they discovered may be the Äpplet, and the second wreck could be either the Kronan or the Scepter.

“We think that some of them were sunk in the area,” Patrik Hoglund, another Vrak archaeologist, told the Guardian. But these ships didn’t capsize because of shoddy engineering or even an enemy attack. Instead, experts believe the Swedish navy intentionally sunk them after they were decommissioned, so their wrecks would function as surprise spike strips to damage approaching enemy ships.

The divers brought back wood samples from the wrecks to send to a laboratory for testing. Once they know when and where the timber came from, they can cross-reference the data with Swedish archives to find out if it matches information from the Vasa.

Even if the warships do turn out to be the Vasa’s long-lost siblings, it’s unlikely that they’ll be salvaged and displayed alongside it, since the Baltic Sea’s brackish waters actually preserve them much better than a museum could.

Sweden isn’t the only nation that boasts a beautiful shipwreck or two—here are 10 other shipwrecks around the world that you can visit.

[h/t The Guardian]

SECTIONS

arrow
LIVE SMARTER